Known histogram-based adaptive gain control (AGC) systems are based on the maximum amplitude histogram bin to control the output video level or use other histogram weighting functions such as using the bin with the greatest number of pixels exceeding a preset maximum for that bin. Those applications have been used in non-intensified cameras based on conventional CCD or CMOS image sensors.
However, such algorithms can suffer performance issues when there is a bimodal distribution of pixel values in the histogram such that the preponderance of pixels are either very dark or very bright with fewer mid-level gray values between, such as might occur when imaging a dark horizon with interfering sky glow or in urban environments. Under such conditions, imagery from known AGC system can have excessive saturation (clipping) of bright scene content, as compared to a scene with no excess dark scene content. In an intensified camera, this leads to shortened tube lifetime, reduced intra-scene dynamic range, and loss of useful scene content near bright sources.